Adjustable venturi throat for the purification of blast furnace gases

ABSTRACT

This disclosure teaches an adjustable venturi throat for dust purification of blast furnace gases, operating at up to sonic velocities with a substantially constant pressure drop, adjusted by dampers having a length of approximately one half the width of the throat. In a preferred embodiment the dampers are streamlined in shape, with the narrower ends swinging in mirror images to form a nozzle curve. The ends may be adapted to form a rollertype closure when the dampers are fully closed.

United States Patent [1 1 Baum [111 3,799,502 [451 Mar. 26, 1974 1 1 ADJUSTABLE VENTURI THROAT FOR THE PURIFICATION OF BLAST FURNACE GASES [75] lnventor:

[73] Assignee: Verfahrenstechnik Dr.-lng. Kurt Baum, Essen, Germany [22] Filed: July 10, 1972 [21] Appl. No.: 269,924

Jiirg Peter Baum, Essen, Germany [30] Foreign Application Priority Data July 17, 1971 Germany 2135840 [52] US. Cl 251/124, 251/212, 266/15, 266/31 [51] Int. Cl. F16k 47/00 [58] Field of Search 251/124, 212, 298, 308; 137/527; 266/15, 16,17, 30, 31

[5 6] References Cited UNITED STATES PATENTS 3,160,385 I 12/1964 Dicesare; 251/212 X 1,357,440 11/1920 Britcher 251/298 1,543,637 6/1925 W011 251/212 X 2,067,120 1/1937 George 251/212 X 3,378,226 4/1968 Naundorf et a1 251/124 X 3,444,669 5/1969 Panzica et a1 266/15 X Primary Examiner-Henry T. Klinltsiek Attorney, Agent, or Firm-Charles E. Baxley, Esq.

[5 7] ABSTRACT This disclosure teaches an adjustable venturi throat for dust purification of blast furnace gases, operating at up to sonic velocities with a substantially constant pressure drop, adjusted by dampers having a length of approximately one half the width of the throat. ln a preferred embodiment the dampers are streamlined in shape, with the narrower ends swinging in mirror images to form a nozzle curve. The ends may be adapted to form a roller-type closure when the dampers are fully closed.

6 Claims, 6 Drawing Figures BACKGROUND OF THE INVENTION Adjustable venturi throats which are known, for instance, for purification of blast furnace gases permit adaptation to varying gas flows while maintaining a constant pressure loss. They have long throat dampers with a closing angle of from to and a practically linear control characteristic. With these dampers a very small angle of rotation effects a considerable change in cross section of the throat. Such a characteristic is unsuitable when operating with very high velocities which can rise up to the sonic region because the control can reverse in an instable region. This region can neither be avoided nor controlled when using the known dampers. The degree of dust removal decreases in this region down to values which are unusable.

The present invention solves the problem of creating a venturi throat with dampers which, within the region of the speed of sound, assure sensitive control necessaryin that region. In accordance with the invention it is possible to develop dampers in such a manner that large angles of rotation change the cross section of the throat only slightly. In this way there is solved simultaneously the problem of regulating the pressure rapidly and precisely in the region of the speed of sound in such a manner that a higher pressure loss than that necessary for purification of the gas is continuously done away with.

With the aid of the new dampers, therefore, when used behind blast furnaces, pressure in the blast furnace throat is also indirectly controlled.

In order to achieve the objects desired, the new venturi throat is so developed that dampers of a length which corresponds approximately to half the width of the throat of the venturi serve to control the cross section of the throat of venturi dust precipitators which are operated up to the region of the velocity of sound.

A further feature consists of streamlined dampers the outer edges of which swing as mirror images to each the throat dampers form a part of the wall of the venturi.

Another improvement resides in the fact that the lengths of the throat dampers are adjustable, for instance by means of bayonet guides.

The new invention results in substantial advances in the art. The increase of the flow in the venturi to sonic speed increases the degree of dust removal considerably and improves the size of particles which can be separated to submicroscopic smallness. Breaking down of pressure or pressure control effect is considerable at these high speeds. The reaction on the control of the pressure in the throat of a blast furnace is in accordance herewith.

The new throat dampers have an extremely short, compact construction, as well as a small angle of closure. However, they may be developed also for longitu dinal displacement and then, if necessary, can be adapted subsequently to desired control tasks.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows the fundamental relationship between damper length and control characteristic.

FIG. 2 serves to explain the special control characteristic of the new invention.

FIG. 3 shows control characteristics for different damper lengths compared with each other.

FIG. 4 is a diagrammatic longitudinal section through an illustrative new throat.

FIG. 5 is a cross section through a throat damper in extended condition.

FIG. 6 is a cross section corresponding to FIG. 5 with the damper in retracted condition.

DESCRIPTION OF PREFERRED EMBODIMENT In detail, from FIG. 1 there can be noted the fundamental formula relationship between the length of a control damper of any desired shape with respect to its control characteristic in accordance with the following derivation.

Derivation of the control characteristic (for any desired length of damper) F=2-c-sinBmax-h F, 2 b L b a max a B=2-c'sinBmax F, F (1 sin B)/sin B max For sin max FIG. 2 reflects this mathematical relationship with respect to the throat dampers in the dimensions in accordance with the invention in order to show the higher value of use corresponding to the derivation.

The derivation of the control characteristic (for damper length one-half throat length):

sin [3 a/c a c sin B F B L 2 c" L FIG. 3 shows this result in particular for the region of high speeds.

In the practical but illustrative embodiment of FIG. 4, a mirror-image arrangement of short throat dampers l is installed swingably in corresponding recesses of a venturi throat 3 as venturis 4 in such a manner that upon complete opening of the dampers the wall 8 of the venturi throat is continued in flush and smooth fashion and continues into the inner wall of the dampers 7. The dampers are shown in dotted line, as can be noted from FIG. 4.

The dampers 1 have a length 2 which corresponds to about half the width of the throat 4. It can furthermore be noted in FIG. 4 that the dampers 1 are of streamlined contour. Their outer edges 5 swing as mirror images to each other to form a nozzle curve 6. Furthermore, FIG. v4 shows that the throat dampers 1 have a closure angle of between 60 and 90. In their closed position, the throat dampers roll on each other in the manner of a roller-type closure.

The rest of the development of the venturi throat is conventional; therefore, it is not necessary to describe it specifically.

FIGS. 5 and 6 show, on an enlarged scale, a throat damper 1 in an embodiment which is enlarged as compared with FIG. 4. It can be seen that the dampers l are divided in two parts. The front ends 5 of the dampers are supported by means of a bayonet guide 9 for longitudinal displacement in the rear swing ends so that the length 2 can be considerably increased or reduced without the shape or the mechanical strength of the damper being impaired. The longitudinal displaceability of the control dampers can also be achieved by other means well known to the man skilled in the art.

It will be evident to those skilled in the art that various deviations may be made from the foregoing preferred embodiment without departing from the main theme of invention set forth in the following claims.

I claim:

1. A venturi apparatus for dust precipitation adaptable to varying rates of flow of gas while maintaining a substantially constant pressure drop at operation up to sonic velocities, having a throat with an adjustable cross-sectional opening controlled by a pair of dampers each mounted pivotally on one end, each of the damp ers having an adjustable length equal at its maximum to approximately one half the width of the throat.

2. A venturi apparatus according to claim 1 wherein each of the dampers is streamlined in shape becoming narrower progressively from the pivotally mounted end to its unmounted end, the dampers pivot in mirrorimage relationships, positioning of the unmounted ends creating the throat.

3. A venturi-apparatus according to claim 2 wherein the dampers have a closure angle of between 60 and 4. A venturi apparatus according to claim 3 wherein the unmounted end of each damper is adapted for cooperatively rolling with the unmounted end of the other damper of the pair to the final closed position of the dampers to form a roller-type closure.

5. A venturi apparatus according to claim 4 with the throat defined by a wall having recesses adapted to receive the dampers, the recesses so shaped that when the dampers are fully open and retracted therein they form substantially continuous surfaces with adjacent portions of the walls.

6. A venturi apparatus for dust precipitation adaptable to varying rates of flow of gas while maintaining a substantially constant pressure drop at operation up to sonic velocities, having a throat with an adjustable cross-sectional opening controlled by a pair of dampers each mounted pivotally on one end, each of the dampers having an adjustable length equal at its maximum to approximately one half the width of the throat, each of the dampers streamlined in shape becoming narrower progressively from the pivotally mounted end to its unmounted end, the dampers pivoting in mirror-image relationships, positioning of the unmounted ends creating the throat, the dampers having a closure angle of between 60 and 90, the unmounted end of each damper adapted for cooperatively rolling with the unmounted end of the other damper of the pair to the final closed position of the dampers to form a roller-type closure, the throat defined by a wall having recesses adapted to receive the dampers, the recesses so shaped that when the dampers are fully open and retracted therein they form substantially continuous surfaces with adjacent portions of the walls. 

1. A venturi apparatus for dust precipitation adaptable to varying rates of flow of gas while maintaining a substantially constant pressure drop at operation up to sonic velocities, having a throat with an adjustable cross-sectional opening controlled by a pair of dampers each mounted pivotally on one end, each of the dampers having an adjustable length equal at its maximum to approximately one half the width of the throat.
 2. A venturi apparatus according to claim 1 wherein each of the dampers is streamlined in shape becoming narrower progressively from the pivotally mounted end to its unmounted end, the dampers pivot in mirror-image relationships, positioning of the unmounted ends creating the throat.
 3. A venturi apparatus according to claim 2 wherein the dampers have a closure angle of between 60* and 90*.
 4. A venturi apparatus according to claim 3 wherein the unmounted end of each damper is adapted for cooperatively rolling with the unmounted end of the other damper of the pair to the final closed position of the dampers to form a roller-type closure.
 5. A venturi apparatus according to claim 4 with the throat defined by a wall having recesses adapted to receive the dampers, the recesses so shaped that when the dampers are fully open and retracted therein they form substantially continuous surfaces with adjacent portions of the walls.
 6. A venturi apparatus for dust precipitation adaptable to varying rates of flow of gas while maintaining a substantially constant pressure drop at operation up to sonic velocities, having a throat with an adjustable cross-sectional opening controlled by a pair of dampers each mounted pivotally on one end, each of the dampers having an adjustable length equal at its maximum to approximately one half the width of the throat, each of the dampers streamlined in shape becoming narrower progressively from the pivotally mounted end to its unmounted end, the dampers pivoting in mirror-image relationships, positioning of the unmounted ends creating the throat, the dampers having a closure angle of between 60* and 90*, the unmounted end of each damper adapted for cooperatively rolling with the unmounted end of the other damper of the pair to the final closed position of the dampers to form a roller-type closure, the throat defined by a wall having recesses adapted to receive the dampers, the recesses so shaped that when the dampers are fully open and retracted therein they form substantially continuous surfaces with adjacent portions of the walls. 